1. Field of the Invention
The present invention relates to a technique for determining noise, and in particular to a technique for determining noise in an image signal.
2. Description of the Background Art
Various techniques have conventionally been proposed to detect and remove noise in an image signal produced by an image sensor such as a solid-state image sensor.
For example, Japanese Patent Gazette No. 5105215 discloses a technique for detecting and removing noise included in chroma components.
Imaging devices using image sensors such as solid-state image sensors may be used as surveillance cameras, which are not limited for use in bright light and may be used in low light.
In the case of use in low light, it is difficult to discriminate between noise and significant components in the image. With conventional noise-detection techniques that unconditionally remove detected noise, which include Japanese Patent Gazette No. 5105215, there has been the possibility that significant components in the image will be misrecognized as noise and removed.
In addition, there is another problem in that although the ratio of noise is high in low light, the conventional noise-detection techniques, which include Japanese Patent Gazette No. 5105215, cannot effectively determine noise and accordingly cannot remove noise satisfactorily.